King crab Legs are already cooked when you purchase them. The majority of Alaska's crab is cooked and blast frozen to secure it's prized taste. They need only to be adequately heated before eating. It is recommended that crab legs thaw overnight in your refrigerator. If you're in a big hurry, king crab can be thawed under cold running water to speed this up. If you place them on a rack in a watertight container, they can drain as they are defrosting.